I've had this issue internally too, and found that only Mikrotik's own S+RJ10 transceivers handle the 2.5/5 Gbps speeds gracefully on their switches. Others som

I've had this issue internally too, and found that only Mikrotik's own S+RJ10 transceivers handle the 2.5/5 Gbps speeds gracefully on their switches. Others sometimes negotiate at 10 Gbps and you get like 1.2 Gbps maximum over the 2.5G interfaces. It's kind of infuriating, to the point I bought a separate dedicated 2.5G switch with 10G uplinks and plugged that over to the Mikrotik with a DAC.